Background and Purpose: There has not been any study regarding atrial systolic function in transcatheter atrial septal defect (ASD) closure. The aim of this study was to survey left atrium ejection force in this procedure in the pediatric age group. Subjects and Methods: This was an observational (before and after) study. Pediatric patients who underwent transcatheter ASD closure using “AMPLATZER” at “Rajaei Cardiovascular Medical and Research Center,” from March to December 2013, were enrolled consecutively. Physical examination and transthoracic echocardiography were performed for the patients before and 12–24 h after the procedure, and left atrium ejection force was calculated. Results: Totally, 63 patients (age: 6.11 ± 3.43 [1–14] years and weight: 21.53 ± 10.79 [9.7–48] kg) were studied. ASD size was 11.43 ± 3.30 (5–22) mm. Left atrium ejection force, before and after the procedure, was 7.19 ± 6.06 (0.33–32.54) kilodyne and 6.30 ± 4.03 (0.5–18.16) kilodyne, respectively (P = 0.28). There was no significant difference between pre- and postprocedure left atrium ejection force in different age group, both genders, types of the device, and ASD size. Postprocedure left atrium ejection force was significantly lower in the patients with large devices (diameter of left atrial disk to body surface area ratio index >40 mm/m2) than smaller device. Conclusion: This study showed that left atrium ejection force after transcatheter ASD closure does not change significantly at early stage, so atrial systolic function is maintained in the presence of the device. In the patients with large device, left atrium ejection force may decrease.

Atrial septal defect (ASD) is the third common congenital heart disease and with the prevalence of 3.8/1000 lives birth and accounts for 6%–8% of congenital anomalies of the heart.[1],[2] For years, surgical closure has been the treatment of choice for ASD. In 1987, King et al. explained transcatheter ASD closure and in 1995, “AMPLATZER occluder device” was presented by Amplatz and Mashura.[2] In recent years, according to general risk of cardiac surgery (anesthesia, intubation, thoracotomy, and hospitalization), there is an increasing interest in transcatheter ASD closure,[3],[4],[5] and consequently, many studies have been performed regarding different aspects of this procedure, but there is not any study regarding left atrium function after transcatheter ASD closure in pediatric patients, so according to considerable role of left atrium function in the heart hemodynamics, also deficiency of relevant studies, we designed this study to survey left atrium ejection force before and after transcatheter ASD closure in pediatric patients.

Subjects and Methods

This was a case series (“before” and after”) study which was performed cross-sectionally. The study population consisted of pediatric patients (1–16 years old) with the diagnosis of ASD, admitted at a university tertiary cardiology hospital, from March to December 2013, who underwent transcatheter ASD closure, using different type of the devices. Method of sampling was “simple” with “consecutive” inclusion. Exclusion criteria comprised any congenital heart anomaly other than ASD, pulmonary hypertension, severe mitral regurgitation, mitral cleft and any known syndrome, and all contraindications of transcatheter ASD closure.

Demographic and clinical data were gathered and recorded. Transthoracic echocardiography was performed by an academic pediatric cardiologist, with 3 and 7 MHZ transducer, before and after transcatheter ASD closure using Vivid 3 echocardiography unit (Medical GE system, USA). Left atrium ejection force was calculated based on Newton's law, as the method of Manning et al.[6] using conventional Doppler indices: left atrium ejection force = 1.3*Mitral valve area* (A wave peak velocity).[2]

Mean of three measurements recorded at patient's left atrium ejection force. After data collection, analysis were performed in SPSS 18 software (IBM, IL, USA) using appropriate statistical descriptive and analytical tools, paired t-test or Wilcoxon test was used for comparison of left atrium ejection force before and after transcatheter ASD closure, and independent test, Mann–Whitney, or ANOVA tests were used for comparison of left atrium ejection force between groups, appropriately. Chi-square test was used for grouped variables. P < 0.05 was considered statistically significant.

Results

Of 65 patients who underwent transcatheter ASD closure from March to December 2013, the procedure was successful in 63 cases (enrolled samples). Forty-four patients (67.7%) were female, more than half of our patients were under 5 years. Data regarding age, weight, ASD, and device size are shown in [Table 1].

Nearly 87.5% of the patients were asymptomatic, among symptomatic patients, palpitation, fatigue, and dyspnea were the main symptoms. There was normal chest X-ray in 76.9% of the patients and also increased pulmonary vascular marking in the others regarding electrocardiogram: there was sinus rhythm in 100% and right axis in 7.7% of the patients regarding mitral valve, there was mitral regurgitation (trivial to mild) in 9.2% and 7.4% of the patients, pre- and postprocedure, respectively, also tricuspid regurgitation (predominantly mild) in 15.4% and 12.7%. The data regarding pre- and postprocedure left atrium ejection force to age group, gender, and indexed ASD sized are shown in [Table 2].

As seen, left atrium ejection force significantly increased with age, whereas there was no significant difference in left atrium ejection force before and after transcatheter ASD closure in all patients, also in subgroups.

For evaluating effect of device size on left atrium ejection force, we defined two indices – ratio of “device left atrium disc,” size to “body surface area” (mm/m2), and “device waist size” to “ interatrial septum size.” We surveyed measures of left atrium ejection force before and after transcatheter ASD closure to these two indices, also to three more common types of the devices [Table 3].

Table 3: Measures of left atrium ejection force before and after transcatheter atrial septal defect closure to two indices of device size and types of the devices

As seen “after procedure,” left atrium ejection force was significantly decreased in the patients with “diameter of left atrial disk to body surface area ratio index” more than 40 mm/m2. There were not any significant differences in left atrium ejection force between three commonly used types of devices.

Discussion

In this study, changes of a hemodynamical parameter of left atrium function (left atrium ejection force) before and after transcatheter ASD closure in pediatric patients were surveyed.

Recently, increasing interest in transcatheter ASD closure, also technical progress in production of more appropriate devices, especially in pediatric age group, has resulted in performing many studies regarding different aspects of the procedure, including hemodynamic indices, such as surveying of right ventricle end-diastolic diameter (the study of Kaya et al.[7]), surveying of myocardial performance index (the study of Salehian et al.[8]), survey of metabolic indices (the study of Giardini et al.[9]), and some other studies.[10],[11],[12],[13],[14] Among these studies, although there were few studies regarding changes of atria after transcatheter ASD closure (“left atrium size” in the study of Salehian et al.[8]), there was not any published study regarding left atrium hemodynamic function.

In this way, gradually since two decades ago, according to different researches and evidence, the role of atria extended from “passive conduit” to other roles such as reservoir, active blood transport, and biochemical activity,[15],[16],[17],[18],[19] so general knowledge and interest about atria, especially left atrium in normal and pathological hemodynamics of the heart, were developed.[20],[21] Different indices can be used for surveying of left atrium function, such as “atrial systolic contribution to the mitral flow” and “pulmonary venous retrograde flow” evaluation of kinetic energy and also left atrial ejection force.[22],[23],[24],[25],[26],[27] Among them, left atrium ejection force is the most common parameter which is used in studies for surveying left atrium hemodynamical function. Evidence have shown that considerable amount of cardiac output (10%–30%), especially during activities, depends on systolic ejection of the left atrium, so changes of left atrium ejection force in different hemodynamical status of the heart may affect the global efficacy of cardiovascular system.[28],[29],[30],[31] There were some studies regarding changes of left atrium ejection force in different situations: the study of Cioffi et al.[32] (like our study) showed that left atrium ejection force increased with age, Triposkiadis et al.[33] studied left atrium ejection force in chronic heart failure and showed that in spite of decreased LA systolic shortening in the condition, because of increased LA size, globally, amount of left atrium ejection force increases, whereas Cioffi et al.[34] showed that increased left atrium ejection force in chronic heart failure is not related to left atrium size. The study of Mattioli et al.[35] indicated that left atrium ejection force is a reliable index for evaluation of returning left atrium mechanical function after cardioversion, Nemes et al.[36] surveyed left atrium ejection force in noncompaction cardiomyopathy, also Jahns et al.[37] Inoue et al.[38] and some others, studies left atrium ejection force in other situations.[39],[40]

Regarding changes of left atrium ejection force after transcatheter ASD closure in pediatric patients, we did not find any published evidence, hence this study is the first in this issue. Our study showed that left atrium ejection force did not change significantly after transcatheter ASD closure, for interpretation of this finding, and it is essential to consider possible factors which may affect left atrium ejection force in this condition; according to left atrium ejection force calculation formula and the evidence regarding effective indices on left atrium ejection force,[28],[29],[30],[31],[32],[33],[34],[35],[36],[37],[38],[39],[40] some factors can be considered for explaining left atrium ejection force changes after transcatheter ASD closure, including elasticity, stretching power, size of LA and LV and also blood volume. Change (decrease) in elasticity due to the presence of device as part of the interatrial septum may decrease left atrium ejection force after the procedure. Furthermore, stretching power from the “device left atrium disc” on muscular plain of left atrium can disturb left atrium systolic contraction and consequently can decrease left atrium ejection force. Considering all these factors, also our findings, while there was some decrease in left atrium ejection force after the procedure, this change was not significant, so it seems that previously mentioned effective factors cannot change left atrium ejection force significantly after transcatheter ASD closure, so based on these findings, it can be concluded that left atrium systolic function as important part of global hemodynamics of the heart is maintained in the presence of device at interatrial septum although more studies can determine the issue more clearly.

Our study also indicates that maintenance of left atrium ejection force after transcatheter ASD closure is true in different age group, both sexes, different types of the devices and different indexed sizes of ASDs.

Regarding effect of device size on left atrium ejection force, our data indicated that postprocedure left atrium ejection force was significantly lower in the device with “left atrium disc size” to “patient's body surface area” equal or more than 40 mm/m2 in comparison to smaller devices (the ratio <40 mm/m2) although there was no significant difference between pre- and postprocedure left atrium ejection force in both groups. This finding indicates that large “left atrium disk size” of the device may be a risk factor for impairment of left atrium function and decreasing left atrium ejection force.

Conclusion

This study showed that transcatheter ASD closure in pediatric age group did not significantly affect left atrium ejection force, hence left atrium systolic function is maintained predominantly; furthermore, the study indicated that using devices with large left atrium disc size may be a risk factor for left atrium ejection force impairment.

There may be some limitations in our study. We surveyed left atrium ejection force at early phase after transcatheter ASD closure (12–24 h) after procedure although the evidence showed that hemodynamic remodeling is initiated at early postprocedure phase, late possible changes of left atrium ejection force after transcatheter ASD closure can be surveyed in the future studies; furthermore, our sample size may be a limiting factor.

Acknowledgment

The authors would like to thank the patients, the parents, and the nurses.

Financial support and sponsorship

This research received no specific grant from any funding agency, commercial, or not-for-profit sectors.